Presses working sheet material conveyed by gripper bars



Nov. 8, 1960 F. LAI JFER 2,959,080

PRESSES WORKING SHEET MATERIAL CONVEYED BY GRIPPER BARS Filed July 11, 1957 Fig.4.

FISHER 1 igg PRESSES WORKING SHEET MATERIAL CON- VEYED BY GRIPPER BARS Frdric Laufer, Prilly, Switzerland, assignor to J. Bobst and Son S.A., Prilly, near Lausanne, Switzerland, a corporation of Switzerland Filed July 11, 1957, Ser. No. 671,336 Claims priority, application Switzerland July 18, 1956 4 Claims. (Cl. 83-206) This invention relates to gripper mechanisms for the conveyance of sheet matter.

To convey sheet material such as paper or cardboard by means of gripper bars intended to insert the sheets between tool bearing platens and then, to remove the worked sheets and so forth is known.

Known gripper bars, which have a flat cross-section, bear on one of their faces, grippers which by way of example are in the shape of flexible strlps. These strips, as a rule are not longer than the width of the face of the associated bar.

The sheets are held between the grippers, which constitute individual jaws, and the face of the bar beanng them, the latter constituting a jaw common to all the grippers. The margin along the edge of each sheet resting on the bar thus cannot be worked, as the press tools can only operate on the surface of the sheet beyond the gripper bar.

It often happens that an appreciable economy of material could be effected if cutting were to continue as far as the very edge of the sheet at certain places which would in no way prevent the clamping from being affected at neighboring points.

In order to achieve this advantage, the press which is provided in accordance with the present invention is fitted with gripper bars provided with grippers comprising two thin superimposed flexible strips, which grip the sheets between them, the clamping part of said grippers extending beyond the bar towards the sheet.

By thin flexible strips are meant, by way of example, steel strips 1 or 2 mm. thick.

The annexed drawing shows an embodiment of the invention given by way of example.

In the drawing:

Fig. 1 is a cross-section of a bar adjacent to a gripper holding a sheet being worked between two tools of a press;

Fig. 2 is a perspective view of the elements shown in Fig. 1; and

Fig. 3 shows a gripped sheet, said sheet being slightly deformed as it is punched.

The sheet 1, which by way of example can be cardboard, is punched along a cutting line by tools borne by an upper platen 2 and a lower platen which is covered by a plate 3. These tools are, by way of example, the cutters 4 and 5 and, on the plate 3, a sheet 6 utilized for make ready.

During the punching operation, the sheet 1 is held aligned in position between the tools by means of the gripper bar 7 and inside the jaws formed by the flexible steel strips 8 and 9.

It can be seen that the two superimposed strips are placed on the upper face of the bar 7 on which they lie flat, while the free extremities of the strips from the jaws gripping the sheet 1. The free extremities project beyond the bar. In working position, these overlapping extremities rest upon the make ready plate 6.

2,959,080 Patented Nov. 8, 1960 As they are quite thin, strips 8 and 9 do not prevent the lowering of the upper tool bearing cutters 4 and 5, the more so as the cutters are fitted with a flexible cover R, see Fig. 3, which may, for example, be of rubber housed in the space 10 and which will be slightly squeezed in the proximity of the grippers.

Whereas hitherto the cutting lines could be placed only beyond the grippers, at 5 (Fig. 1) for instance, to obtain cutting 5' (Fig. 2), the device just described enables the cutting lines to be placed between the grippers at 4 (Fig. 1) in order to have the cutting efiected at 4' (Fig. 2) in such a manner that it extends as far as the very edge of the sheet.

It is obvious that at the actual point where the clamping is effected, the sheet will not rest absolutely flat against the lower tool. It will lie away from this surface at a distance corresponding to the thickness of the gripper strip 8, as shown in Fig. 3. This deformation is, however, so slight that the sheet 1 can be worked very close to the gripper by means of the cutter 4.

The grippers 8 and 9 are fixed by means of screws 11 and nuts 12 and are opened by pistons 13 lifting the upper strip 9. The screws and pistons traverse the bar which is drilled, for example at 14 and 15, so as to permit the grippers to be repositioned at will or eliminated at any point chosen to effect a cutting, such as at 4. Due to the movable quality of the grippers, cutting can be effected without making allowance for the said grippers.

It is obvious that the grippers described by way of example could be designed in a different form.

For instance, strip 8 could have a thicker part fitting in a transversal groove on the upper face of the bar and terminating in a thin nose serving as a jaw and positioned as already described on the plate 6 of the lower tool.

Finally, it is obvious that the terms lower and upper as used here have only a relative value as the whole system including the mechanism and the functions of the machine can be rotated through What I claim is:

1. Sheet processing apparatus comprising means for operating on said sheet, said means including members having a relative reciprocating movement towards and away from each other, a device on at least one of said members forperforming an operation at an edge of said sheet with the members displaced towards each other, resilient means on at least one of said members and between the latter, gripper apparatus movable independently of the first said means, said gripper apparatus comprising a gripper bar, at least one pair of superimposed flexible strips mounted transversely of said bar and including portions extending beyond the bar in yieldably engaging relation for gripping said edge of the sheet, said strips being biased together in close relationship for gripping said sheet and forming together a flat structure adapted for being accommodated between said members, said strips gripping said sheet over an area which in small compared to that of said sheet, and means for positioning said bar adjacent the first said means with the extending portions of said strips between said members, with the latter displaced towards each other, said resilient means yieldably accommodating said strips to permit said device to perform said operation with the strips between said members.

2. Apparatus as claimed in claim 1, wherein the bar has opposite faces, one strip resting against and being fastened to one of the faces, the other strip having a U-shaped extremity accommodating the gripper bar and being connected to at least the other of the faces.

3. Apparatus as claimed in claim 1, wherein one strip is interposed between the other strip and the bar, the interposed strip and the bar defining corresponding openings, comprising a piston slidable in the openings to displace said other strip.

3 4 4-. Apparatus as claimed in claim 1, comprising means 1,079,218 Curtis Nov. 18, 1913 for,adjustab1y fastening said strips on said bar. 1,082,986 Wilder- Dec. 30, 1913 1,336,598 Throop Apr. 13, 1920 References Cited in the file of this patent 2,572,691 Bobst Oct. 23, 1951 UNITED STATES PATENTS 6 FOREIGN PATENTS 517,653 Meisel 3, 1894 351,285 Great Britain June 25, 1931 

